Chapter 8, Problem 22P

(a)

To determine

To Find:The maximum torque that the person exerts.

Answer to Problem 22P

  $\tau =92\text{mN}$

Explanation of Solution

Given information:

Radius of circle $\left(r\right)=0.17\text{m}$

Mass of person $\left(m\right)=55\text{kg}$

Formula used:

Maximum torque

  $\tau =F\times r$

Here, $r$ is the radius of circle.

  $m$ is the mass of person.

Calculation:

  $\tau =F\times r$

  $\begin{array}{l}=mg\times r\\ =\left(55\times 9.8\times 0.17\right)\text{mN}\\ \tau =92\text{mN}\end{array}$

Conclusion:

The value of the torque is $\tau =92\text{mN}$ .

(b)

To determine

The way in which the person can exert more torque.

Explanation of Solution

Introduction:

Maximum torque

  $\tau =F\times r$

Here, $r$ is the radius of circle.

  $m$ is the mass of person.

Person could exert more torque by pushing down harder with her legs, raising her center of mass. She could also pull upwards on the handle bars as she pedals, which will increase the downward force of her legs.

Conclusion:

Pedalling results in increasing the downward force of her legs.